- Experimental Procedure Part A Reaction At Elevated Temperature Dissolve 2 0 G Of Semicarbazide Hydrochloride In A Solut 1 (460.09 KiB) Viewed 42 times
- Experimental Procedure Part A Reaction At Elevated Temperature Dissolve 2 0 G Of Semicarbazide Hydrochloride In A Solut 2 (76.29 KiB) Viewed 42 times
weight for part B: 2.55g (cyclohexanone)
EXPERIMENTAL PROCEDURE Part A: Reaction at elevated temperature Dissolve 2.0 g of semicarbazide hydrochloride in a solution of 4.0 g of sodium hydrogen carbonate (NaHCO3) in 50 mL of water in a 250 ml round bottom flask. When the effervescence ceases, add 1.6 mL of furfural and 2.0 mL of cyclohexanone and heat the reaction mixture on a steam bath (steam bath set up is 250 ml round bottom flask placed on top of a beaker with boiling water) for one hour. Cool the mixture in an ice bath and collect the precipitate by suction filtration. Recrystallize it from a minimum volume of hot ethanol (approx. 20 mL of ethanol per gram of product) (students are advised to start heating up ethanol at the start of the experiment). Identify the semicarbazone, from its melting point (by comparing with the authentic semicarbazones, cyclohexane semicarbazone-166- 167°C and furfural semicarbazone is 201-201°C) Melting points Record the melting point of product from Part A & Part B and find their identity by comparing with above given melting points. Part B: Reaction at room temperature Note: You can start this reaction during the waiting time for reaction (a). Repeat the experiment in the way described under (a), only this time, do not heat the solution. Instead, gently shake the 250 ml round bottom flask for 5 minutes at room temperature before isolating the product. Recrystallize the semicarbazone from hot ethanol (about 1.0 mL/g) and identify it in the manner described above.
Theoretical and Percentage Yield Calculations Complete the following calculations in the tables below: (Give all answers to 3 significant figures except where specified). Moles of fufural used Moles of cyclohexanone used Moles of semicarbazide hydrochloride Therefore the limiting reagent is: Calculation Expected moles of product Molecular weight of product (give your answer to 2 decimal places) Theoretical yield (g) Yield obtained (g) Calculated % yield (give your answer to the nearest whole number) 0.0193 0.0193 0.0179 semicarbazide hydrochloride Cyclohexane semicarbazone 1.25 Furfural semicarbazone 2.25